Solid-state battery

A solid-state electrochemical cell (SSEC), comprising:

• (a) a positive electrode layer comprising an active material and a sulfide catholyte, wherein the active material is selected from LiNixMnyCOzO2, and LiNixAlyCOzO2, wherein x+y+z is equal to 1;
• (b) a single ion conducting, solid-state buffer layer, wherein the single ion conducting, solid-state buffer layer comprises LSTPS, wherein LSTPS is an electrolyte material including Li, Si, P, Sn, and S chemical constituents, wherein the buffer layer has a thickness of greater than 1 μm to 15 μm;
• (c) a borohydride bonding layer;
• and
• (d) a lithium-stuffed garnet layer, wherein the lithium-stuffed garnet layer comprises a lithium-stuffed garnet selected from LixLayZrzOt·qAl2O3, wherein 4<x<10, 1<y<4, 1<z<3, 6<t<14, and 0≤q≤1;
• wherein:
• the buffer layer is a layer in contact with the positive electrode layer;
• wherein the borohydride bonding layer is between and in contact with the lithium-stuffed garnet layer and the buffer layer in contact with the positive electrode,
• wherein the borohydride bonding layer comprises a borohydride composition comprising:
• A·(LiBH4)·B·(LiX)·C·(LiNH2),
• wherein X is fluorine, bromine, chlorine, iodine, or a combination thereof, and
• wherein 3≤A≤6, 2≤B<5, and 0≤C≤9.